EP1099429A1 - Interbody Fusion cage with crescent shaped lips (duckbill shaped) - Google Patents

Abstract

The ring has a duck-bill shaped edge which is introduced between two lower vertebrae. The block comprises a ring (5) which is has an oval shape, with the hole passing vertically through the block. One of the ends of the block is reduced in thickness in a duck bill shape (6,8,9) in order to facilitate its insertion between two vertebrae. The duck bill shape includes a common edge (6) which joins together the two sides (8,9) which form the leading edges of the two opposite faces of the ring. The duck bill extends through a length which is between one fifth and one quarter of the total periphery of the ring. The height of the duck bill is between a quarter and third of the total height of the ring.

Description

The invention relates to an interbody fusion cage, and particular to a cage which extends in a longitudinal direction (D) to be inserted between two vertebral bodies by impacts exerted on one end (7) from the cage.

The cage is inserted between the adjacent vertebral bodies to restore in a patient a suitable height and statics of a disc space, in particularly from the lumbar region of the spine.

We know from document FR 2 762 779 a fusion cage interbody extending in a longitudinal direction having a shape broadly parallelepiped. The side walls of the cage are flat for reduce the overall dimensions of the cage and allow two cages to be inserted into the disc space in order to increase the stability of the two vertebral bodies.

The cage is inserted between the vertebral bodies by two bearing surfaces opposite and convex each to follow the configuration naturally concave disc space. By this means, the contact surface between the cage and the two vertebral bodies and we ensure a more stable spacing of the disc space.

The cage is pierced with openings to allow a bone graft arranged inside to merge with the vertebral discs. In the example described in the aforementioned document, the opposite and convex bearing faces have a oblong opening which crosses the cage perpendicular to the direction longitudinal to create communication between the two vertebral bodies. This opening allows the graft to create a bony bridge between the vertebral bodies, the patient's anatomical disc spacing being restored by the cage. The walls flat sides also have openings leading to the opening oblong to promote blood supply to the bone graft. These openings also help strengthen the bone bridge between the vertebral bodies.

The cage is inserted between the vertebral bodies by applying impacts on one of its ends. However, despite the convex shape of the opposite bearing surfaces, impaction can lead to breakage of one or the other of the vertebral bodies, and particularly the anterior bony edges of these when, as usual, the cage is inserted by way posterior.

We also observe that some cages after insertion tend to move under the action of the vertebral bodies, particularly in the opposite direction to insertion.

The object of the invention is to provide an improvement to the cages existing by overcoming the drawbacks described above.

To this end, the subject of the invention is an intersomatic fusion cage extending in a longitudinal direction to be inserted between two bodies vertebral by impacts exerted on one end, characterized in that the opposite end in the longitudinal direction is shaped like a nose or beak duck to facilitate insertion between the vertebral bodies.

When the cage is inserted, the end shaped like a nose or beak duck easily enters the disc space and gradually spreads the two adjacent vertebral bodies. In this way, the risk of fracture of the vertebral bodies at the time of the impaction.

In addition, it was found that moving the cage in the opposite direction opposed to insertion was due to the action of the anterior bony edges of the bodies vertebrae and relative movements of adjacent vertebral bodies, particularly in the postoperative phase where intersomatic fusion is not still realized. According to the invention, the duckbill allows the end of the cage to be placed between the anterior bony edges. In this way, the efforts they exercise on the cage no longer tend to move it in the opposite direction to the insertion.

According to a particular embodiment of the invention, the duckbill includes a common lip joining two notches formed in the two opposite support faces of the cage. This embodiment allows advantageously to form the notches by machining in bearing faces initially not indented. It is however possible to produce the bearing faces and the notches in a single operation, for example by molding.

Preferably, the duckbill extends over a fraction of the length between one fifth and one quarter of the total length of the cage. This interval takes into account the statistical dispersion in humans of the edges bone in the vertebral bodies.

Preferably also, and for the same reasons, the lip of the beak of duck has a height that is between a quarter and a third of the height between the opposite support faces of the cage.

In the aforementioned document, it is provided that the cage has angles external rounded to avoid possible damage to nerve roots and others soft tissue. According to a preferred embodiment of the present invention, the cage angles are not only rounded but broken at a bevel. This shape further reduces the risk of nerve root trauma during removal from the cage.

- La figure 1 est une vue schématique en perspective de la cage intersomatique.

- La figure 2 est une vue en plan de dessus de la cage.

- La figure 3 est une vue en plan de côté de la cage.

- La figure 4 est une vue en coupe partielle d'une extrémité de la cage sur laquelle on exerce des impacts lors de l'insertion.

- La figure 5 est une vue de côté montrant de façon schématique la cage des figures 1 à 4 en position intercalée entre deux corps vertébraux.

Other advantages of the invention are highlighted with the detailed description of the invention illustrated by the drawings.

- Figure 1 is a schematic perspective view of the interbody cage.

- Figure 2 is a top plan view of the cage.

- Figure 3 is a side plan view of the cage.

- Figure 4 is a partial sectional view of one end of the cage on which impacts are exerted during insertion.

- Figure 5 is a side view schematically showing the cage of Figures 1 to 4 in the interposed position between two vertebral bodies.

An intersomatic fusion cage extends, Figures 1 to 3, along a longitudinal direction D to be inserted between two vertebral bodies during a spinal surgery in humans, particularly in the lumbar region of the spine.

The cage is generally part of a rectangular parallelepiped. Through simplification measure, the qualifiers upper, lower, lateral, anterior and posterior will be used by analogy with the six faces of said parallelepiped rectangle, when the cage is in position in the intervertebral space, like this is illustrated by figure 5. In this figure, the part on the right represents the face anterior, while the part on the left represents the posterior face. The cage is interposed between two vertebral bodies 23 and 25. To increase the stability of vertebral bodies, it is planned to insert two cages parallel one with respect to the other in the same disc space. Also shown in Figure 5 is a healthy intervertebral disc 27 between two vertebral bodies 23 and 29. So schematically, Figure 5 illustrates each vertebral body with a pedicle 31 and a prickly 33.

The cage includes two flat side walls 18 and 19 and is inserted between the two vertebral bodies 23 and 25 by two upper bearing surfaces 4 and lower 5 opposite and convex each to follow the configuration naturally concave of the disc space. Openings 17 and 20 are provided to allow an internal bone graft to merge with the vertebral discs. In the example which is described, the opposite bearing faces 4 and 5 and convex have an oblong or ovoid opening 17 which crosses the cage perpendicular to the longitudinal direction D to create a communication between the two vertebral bodies. The flat side walls 18 and 19 have also openings 20 leading to the oblong opening to favor blood supply to the bone graft.

The cage is inserted between the vertebral bodies by applying impacts on a posterior end 7.

According to the invention, the anterior end 2, opposite in the direction longitudinal D at the posterior end 7, is shaped like a duck's nose or beak 6, 8 and 9 to facilitate the insertion of the cage between the vertebral bodies 23 and 25.

In the illustrative example of the invention, visible in FIGS. 1 and 3, the duckbill comprises a common lip 6 uniting notches 8 and 9 formed in the two upper and lower bearing faces 4 and 5. The lip 6 has also a convex profile and advantageously has broken angles in bevel 13 and 14.

As indicated above, when inserting the cage, the end shaped like a duckbill easily enters the disc space and spreads gradually the two adjacent vertebral bodies without hitting them at a sharp angle. In this way, the risk of body breakage is considerably reduced vertebral at the time of the impaction.

In addition, the duckbill allows the end of the cage to be placed between the anterior bony edges 11 and 12 of the vertebral bodies. In this way, the efforts they exert on the cage no longer tend to move it in the direction opposed to insertion.

In other words, when the interbody cage is placed in the intervertebral space, the bone edges 11 and 12 that are encountered on the faces internal and anterior vertebral bodies are housed on both sides at the level of the notches 8 and 9 of the duckbill. The configuration of the end of the cage therefore provides anatomical support for the upper and lower faces 4 and 5 on the internal walls of the vertebral bodies 23 and 25 without creating discomfort at level of the bone edges 11 and 12.

Preferably, as can be seen in FIG. 3, the height h of the duckbill lip 6 is between 1/4 and 1/3 of the height H measured between the upper 4 and lower 5 bearing faces of the cage.

In the embodiment illustrated by the figures, the duckbill extends, in the longitudinal direction D, over a length I between 1/5 and 1/4 of the total length L of the cage measured between the anterior ends 2 and posterior 7.

Advantageously, the bearing faces 4 and 5 have angles 16 broken at a bevel on the side of the posterior end 7. In this way, we avoid traumatize the nerve roots when removing the cage.

The insertion of the cage into the intervertebral space is commonly performed using an impaction tool engaged with the posterior end 7.

Advantageously, as visible in FIG. 4, a tapped hole 24 is designed to receive a threaded rod. We prefer a terminal hole or without light, that is to say a hole which does not open into the oblong opening 17, for prevent the migration of bone fragments through the tapped hole which could cause compression of the nerve roots. 9. During insertion, we exercise impacts on a threaded rod screwed into the threaded hole 24 of the end 7 opposite the end 2 shaped like a duckbill.

The cage according to the invention is made of a biocompatible material, like for example a titanium alloy. As stated earlier, notches can be formed by machining the bearing surfaces initially not indented, or by simultaneous molding of the faces and indentations as well as of the common lip.

Advantageously, the opposite bearing faces 4, 5 have on the surface a pattern of roughness 21 to promote attachment to the bodies vertebral. We prefer a streak pattern, advantageously checkerboard, made by laser beam.

Claims (9)

Interbody fusion cage extending in a longitudinal direction (D) to be inserted between two vertebral bodies (23, 25) by impacts exerted on one end (7), characterized in that the opposite end (2) along the longitudinal direction (D) is shaped like a duckbill (6, 8, 9) to facilitate insertion between the vertebral bodies (23, 25). Intersomatic fusion cage according to claim 1, characterized in that the duckbill comprises a common lip (6) joining two notches (8, 9) formed in two opposite bearing faces (4, 5) of the cage. Intersomatic fusion cage according to claim 2, characterized in that the duckbill extends over a fraction of length (I) between a fifth and a quarter of the total length (L) of the cage. Intersomatic fusion cage according to claim 2, characterized in that the lip (6) has a height (h) which is between a quarter and a third of the height (H) between the opposite bearing faces (4, 5). Intersomatic fusion cage according to claim 2, characterized in the lip (6) has angles (13, 14) broken at a bevel. Intersomatic fusion cage according to claim 1, characterized in that the opposite bearing faces (4, 5) have a surface roughness pattern (21). Intersomatic fusion cage according to claim 1, characterized in that the end (7) on which the impacts are exerted during the insertion comprises a socket (24) for fixing an impaction tool. Intersomatic fusion cage according to claim 7, characterized in that the fixing socket is a tapped hole (24) designed to receive a threaded rod. Intersomatic fusion cage according to claim 8, characterized in that the tapped hole (24) is a blind hole.

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